


Pranking the Algorithm

by PrettyPinkCupcake



Category: Harry Potter - J. K. Rowling, Rigel Black Chronicles - murkybluematter
Genre: Fanfiction of Fanfiction, Female Harry Potter, Inspired by The Rigel Black Chronicles, Maybe a ruse reveal?, Pranks, Rigelverse, Set after chapter 12 of Futile Facade, The Arithmancy Matching Algorithm, The Fade
Language: English
Status: In-Progress
Published: 2020-12-07
Updated: 2020-12-07
Packaged: 2021-03-09 18:21:05
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 6,598
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/27930667
Author URL: https://archiveofourown.org/users/PrettyPinkCupcake/pseuds/PrettyPinkCupcake
Summary: [Fanfiction of murkybluematter's Rigel Black Chronicles.  Set after chapter 12 of Futile Facade.]Not even in his wildest dreams could Tom Riddle have imagined what the fallout from the 5th task of his True TriWizard Tournament would lead to.  Fred and George Weasley were horrified by the cruelty of the tower climb and what poor Rigel and the other contestants were subjected to.  In retribution they resolve to prank Tom Riddle and start planning the greatest prank of all time, co-opting Rigel Black into their new project.  Rigel is a source of unexpectedly useful information.Support for the prankster's aims emerges from unexpected sources; not all dark Purebloods are happy with Riddle's plans.  Edmund Rookwood is particularly upset at the Arithmancy Matching Algorithm, fearing that it will upset his long awaited wedding to Alesana Selwyn, Hermione's research with Rigel and Archie for a solution to the Fade could abrogate any need for a marriage law, and there is potential that Operation: Restore Regulus could change Regulus Black's allegiance.
Relationships: Harriet Potter | Rigel Black & Arcturus "Archie" Black
Comments: 29
Kudos: 95
Collections: Rigel Black Chronicles Appreciation





	Pranking the Algorithm

**Author's Note:**

> This will only make sense to fans of murkybluematter's Pureblood Pretense, Serpentine Subterfuge, Ambiguous Artifice and the Futile Facade.
> 
> If you haven't read these works, you've missed something significant in the world of Harry Potter FanFiction, so what are you waiting for? Read them!

##  _Chapter 1_

“I don’t think you understand, Aldon,” hissed Edmund Rookwood, his voice perhaps louder than he intended so that he could be heard over the celebratory noise in the common room. “Lord Riddle’s precious algorithm doesn’t support me marrying Alice.”

“But it’s always been you and Alice,” Rosier replied, his tone somewhat bitter, no matter how much Rosier thought he’d hidden his feelings. “Besides, you’ve already sent out the invitations. And your wedding is only three months away.

“Not if the marriage law is passed! I need someone to help me fix this. Please. I can’t lose Alice.” The desperation in Rookwood’s voice was palpable.

“Shh. I don’t think that the Slytherin common room is the most appropriate place for this conversation,” responded Rosier. “And certainly not now.”

“Like anyone else cares,” Rookwood said sourly. “They’re all too busy celebrating Rigel’s win.”

“Yeah,” muttered Rosier. “Everyone but Rigel.”

They turned and looked at the apparently unconscious figure slumped in the comfortable armchair beside the sofa they were sitting on. It appeared that the man of the hour had finally succumbed to exhaustion. 

Rigel had been more than happy to return to the Slytherin dungeons with Draco and Pansy after he’d recovered sufficiently from the fifth task, preferring familiar surroundings and the company of his friends to the tournament’s medical tent and tournament officials. 

Once back in the Slytherin dungeons he hadn’t wanted to be left alone. Still recuperating from the mind altering draught he’d been forced to take, Rigel had been happy to sit quietly in an out-of-the-way corner, content to watch while others celebrated around him. 

Draco and Pansy had been fiercely guarding their friend all evening, and Rookwood and Rosier had joined the cordon of Rigel’s fourth year friends shielding him from the rest of the rowdily celebrating Slytherins. 

But now Draco had gone in search of refreshments while Pansy was currently two seats over chatting with Millicent Bulstrode, no doubt discussing the tournament, leaving the sleeping champion with Rookwood and Rosier.

“And us,” muttered Rookwood. 

Rosier gave him a friendly punch in the shoulder. “You should be happy with Rigel’s win. He’s now in an almost unassailable position. And if Rigel wins, no marriage law. No algorithm. Nothing to stop your wedding.”

Rookwood just looked at him. 

“Yeah. Right.” His tone suggested that Rosier must believe in the tale of the Three Brothers, the Unbeatable Elder Wand, the Resurrection Stone and Death’s Cloak of Invisibility, not to mention muggle myths of Santa Claus and the Easter Bunny, to really believe that.

“You know as well as I do that Lord Riddle doesn’t gamble unless the odds are heavily stacked in his favour. _You’re_ the one who told Rigel that.”

Rosier sighed. “Perhaps. Sometimes I just wish I looked at things with Rigel’s optimism rather than my cynicism.”

“Not sure I’d call Rigel optimistic. At any rate, I just wish there was something I could do - I just want to marry Alice. It’s all I’ve ever wanted.”

“Are you sure the algorithm doesn’t support you and Alice?”

“Absolutely. I thought I’d told you that Father’s the Unspeakable in charge of the project. After he had a quiet chat with me, I, ah, borrowed a copy of the algorithm. I’ve run it multiple times.” Rookwood sighed.

“Maybe I can make better sense of it. I’m well aware that you prefer creatures and plants to Arithmancy, whereas you seem to have forgotten that I’m planning on completing a Mastery in Experimental Theory next year.”

Rigel stirred quietly in the armchair in the corner before falling into a deeper state of unconsciousness. The voices around him drifted off and became unintelligible background noise.

But that didn’t stop the ancient entity in Rigel’s head. After the attack on their shared mindscape earlier in the day, the Dominion Jewel had vowed to itself to take a more active role in protecting his host, and it had taken careful note of key aspects of the conversation it had just overheard. 

The centuries had taught Dom that knowledge was power, and knowledge of the plots of Rigel’s enemy - or was it nemesis? To Dom, neither word really described Riddle - was invaluable information.

\- - - - - - - 

“I don’t think you appreciate how difficult it’s going to be when we have to swap back,” Archie moaned through the mirrors after hearing Rigel expound happily about her recent free brewing exploits with Master Snape. Rigel had just finished cleaning up her lab when the mirror call from Archie came through.

The free brewing session had been Snape’s “gift” to her after once she’d finally recovered from all the effects of the hallucinatory mind fuck that had been the fifth task. It had taken her the entire day following the tower climb before she felt truly back to normal.

Snape had been been furious when he’d found out that it was Matheus Sousa, an untested sixth year student who was “on leave” from Castelobruxo (only so he wouldn’t be expelled and could return for his final year), who’d been asked to brew the Draught of Delirium. Not that he was anymore pleased with the choice of brew than he was with the brewer. 

“I’m never going to be able to do all the things Rigel’s done,” Archie moaned. “If only I wasn’t the only Black Heir, I’d run away to America with Hermione. We could research and cure obscure diseases to our heart’s content. No need to worry about the Wizengamot, dark Pureblood politics, or Black legacies. But I can’t do that. Not to Dad.”

“Sirius doesn’t care. He just wants you to be happy.”

“He cares more about the House of Black than you think,” said Archie darkly. “Why, _why_ , couldn’t Uncle Regulus have had children? Then I wouldn’t be the only option as the Black Heir. At least you’ve a sister if you don’t want to continue the Potter line.”

Something tugged at Rigel’s mind. A memory…

She must have had a strange look on her face, as Archie suddenly sat up. “Ha-Rigel. Rigel. Rigel! Are you okay?” there was a tinge of panic in his voice. “You’re not suffering a flashback to the tower are you?”

“What? No. I’m ok,” she replied thoughtfully. “I was just trying to remember something… There’s a reason Regulus hasn’t married and had children. He can’t.”

“Can’t?” queried Archie. “He’s a wizard. Even if he wanted to marry another wizard, he could still have children. Magic, remember?”

“It’s not that,” Rigel replied, inwardly wincing at the memory of Regulus’s rather crass comment that Sirius could get together with his werewolf and have a litter. 

“I overheard something about a curse. A dark magic curse. Apparently something Walburga did to Regulus. Regulus and Sirius hoped that it would fade, but it hasn’t.”

“Overheard? You just happened to overhear this?” Rigel could hear the teasing in Archie’s voice. 

“All right,” she snapped. “Maybe I was eavesdropping. Just a bit. So what?” she asked a tad defensively. “It’s not like you never eavesdrop.” 

Why was she being defensive? Rigel never used to worry about the morality or otherwise of overhearing other people’s conversations. Though admittedly, eavesdropping on Riddle that first Malfoy garden party (and worse, being caught eavesdropping on Riddle) hadn’t been her best decision, all things considered, and with the benefit of hindsight. 

“Aaand that’s why you’re still having problems with your animagus transformation. You need to accept _all_ the traits of your animal - and that includes the mischievous, eavesdropping ones.”

“Yeah yeah.” Her lack of success transforming into her raven form was something she’d worry about later. Along with the gazillion other things that were consuming her energy, many of which like Riddle and the tournament, she could happily do without.

“It was at Sirius’s party when you were in Darien Gap. Otherwise I would have already told you. In fact, you probably would have heard their conversation with me.”

“Was there anything else you heard then that maybe I need to know?”

Rigel cast her mind back to that conversation. 

“Maybe… Yes. Now that I think about it, maybe it’s all linked together…” her voice trailed off. 

“Well,” said Archie impatiently, “what is it?”

“I got the impression then that maybe there was more to Walburga’s madness than we realised.”

“You mean she wasn’t just a crotchety, bigoted Pureblooded hate filled shrew spilling vitriol at everyone who disagreed with her?”

Rigel was surprised at the depth of Archie’s emotion - Walburga was his grandmother - and it must have shown on her face. 

For someone who was so remarkably good at hiding her emotions from everyone else she dealt with, when it came to those she could trust (read: Archie), she clearly let loose. 

“What? I’m sure you don’t forget what her portrait said to you that time in the Grimmauld attic. I don’t, and I wasn’t the one she was attacking. I might have been only seven, but I remember. I was ashamed to be her grandson.”

“I do remember,” Rigel said slowly. “I had nightmares for weeks. But something Sirius said to Regulus made me wonder if Walburga wasn’t suffering from severe, untreated, depression as a result of the miscarriages she’d had. Or Faded children. Or stillbirths. Sirius didn’t specify.”

“Even if she was suffering from depression, it doesn’t mean she had a free pass to act like a pig’s arse.”

“I didn’t say that. But I’ve been thinking about the Fade,”

“Good! Reading Hermione’s notes too, I hope,”

Rigel rolled her eyes. 

“Of course. They’re very detailed, and she’s got some original ideas that require further investigation. She’s very clever.”

“She’s brilliant,” sighed Archie. Rigel just rolled her eyes.

“You’re one smitten kitten. But back to the Fade. I’ve been thinking about the toll on families. You just said how you didn’t want to be the only option as heir.” 

Rigel silently thanked her parents for Addy. With a sister, the pressure on her to keep the Potter line going was reduced. Which was just as well, because she didn’t plan on having children. Not at this point, anyway. She had a Mastery to obtain, potions to brew, and Shaped Imbuing to explore. 

“So think, Archie, if that’s how you feel, how must all those Pureblood women feel, with all that pressure to deliver the next generation, only to fail painfully? Alesana Selwyn and Millicent Bulstrode both lost siblings. It’s not something anyone talks about, but if it is ever touched on, you can see the pain on their faces, hear it in their voices. Pansy doesn’t think she can have a career; she’s worried about not being able to produce the requisite heirs if she doesn’t have her first child soon.”

“What does this have to do with Walburga being a pig’s arse?” Rigel couldn’t help but smile at that. Archie clearly knew more than she’d realised about how badly Walburga’s dreadful comments had affected her. 

“Just that Walburga’s depression might have made her desperate, and in her desperation she might have done something dangerous. Something that harmed Regulus, even if she didn’t mean it.”

“Are you saying that _Walburga_ is the reason Regulus can’t have children?”

“Well, apparently that’s what Sirius and Regulus think. Something about a dark curse that they thought would fade.”

“My grandmother, Regulus’s _mother_ , is the reason Regulus can’t have children?” Archie was (rightly) horrified. “How twisted is that?!?”

“It is twisted - but so twisted that it doesn’t make any sense. Walburga desperately mourned the children she lost. So much that she treated the ones who survived badly. Under what circumstances could she possibly be so angry that she would prevent her son from giving her grandchildren?”

“So what are you suggesting?”

“That there’s a lot more to the story than Sirius and Regulus know. Hermione’s analysis showed that those at the greatest risk of the Fade are Pureblood for more than four generations. Orion and Walburga were both Blacks. Maybe Walburga did something to try to circumvent the Fade. Sirius mentioned something about a black ritual in his response to Hermione. But what if it didn’t quite work? What if Walburga’s ritual accidentally left Regulus unable to have children? What if she was ashamed about that? She might have made something up about a curse to hide her actions. And, if the Fade is all about magical cores not working properly, if Walburga did something that affected Regulus’s core, then…” Rigel trailed off, thinking.

“Then what?”

“Then I might be able to see what’s wrong with Regulus by travelling into his core. Dumbledore recently reminded me that I can do something no other healer can. I can travel into people’s cores.”

Archie shuddered. He still remembered his ill advised effort to enter Harry’s core, and how Harry’s magic … _bit_ him, for want of a better description. 

“If what Walburga did was because of the Fade and she somehow affected Regulus’s core, maybe by looking at Regulus’s core I could diagnose why Regulus can’t have children.”

“Are you saying you can heal Regulus? Restore his reproductivity? Give the Black family another choice of heir?”

“No… maybe... I don’t know. What we find out about Regulus might help us with our investigations into the Fade. So I _do_ think we should investigate further. If we could help him, all the better.”

“You don’t particularly _like_ Regulus.”

“Not really. Neither do you. He doesn't particularly like me. Not that Rigel needs Regulus’s approval. But as I told Caelum,”

“Caelum Lestrange?!?” Archie interrupted. 

“Yes, Caelum Lestrange. How many other Caelums do we know of? Caelum might be a bigoted jerk, but he’s not a bad brewer. I think there’s hope that he could learn to be not such a bigoted jerk. I’m working on him.”

Archie rolled his eyes at her. 

“So what did you tell Caelum?” 

“After the Guild Open House I told him that the more enemies I can turn into friends, the easier my life will be in the long-run.”

“Can’t say I disagree with you, but… Caelum? Caelum Lestrange? Son of Bellatrix? Son of the one cousin my father absolutely detests?”

“Yes, that Caelum Lestrange. And making friends out of enemies applies to Regulus too. Regulus is high up in the SOW party. It’s why Sirius was estranged from him, after all. It would be nice if Regulus wasn’t working against us. And ... ” her voice trailed off. 

“And what? Harry, what aren’t you telling me?” Archie asked worriedly. 

“Regulus is active in the Lower Alleys. He did the wards for the free dueling tournament.”

“Wards Master Regulus Black, high up in the SOW party, my snooty dark _Pureblood_ uncle, proud of his lineage in the House of Black, did the wards for a _free dueling_ tournament in the _Lower Alleys_?!?” Archie was incredulous. 

“I thought I told you before.”

Archie shook his head. “No Harry, you didn’t.”

“Oh. Oops. It was when you were in the Darien Gap. And it wasn’t like Regulus did the wards for free. Leo paid him. Quite a bit, according to Aled Flint. Regulus Black is not cheap, but he has a reputation for quality and discretion. And Leo told me that he’d commissioned Regulus to do the wards when the Dancing Phoenix was rebuilt.”

Archie facepalmed. “Please tell me he didn’t see you, Heiress Potter, daughter of the Head Auror, free dueling in that tournament.”

Harry frowned. “If he did, I don’t think he recognised me. I was wearing a hat and goggles. I did see Regulus on the day of the final bout, and the wards weren’t due to come down till the next day, so I think he at least watched some of the tournament. Maybe even one of my duels. When Draco was speaking to him about dueling, Regulus did seem to know about my Fortis shield bubble of doom technique.”

Archie facepalmed again. Facepalming seemed to be a thing with him at the moment. 

“But I’m pretty certain I managed to convince him that you and I reverse engineered that trick after Harry saw it demonstrated somewhere down Diagon Alley when she was checking out apothecaries for bargains.” She was babbling again and both she and Archie knew it. 

“Ok, that’s enough,” Archie sighed. “You’ve worried me that Regulus will see through the ruse - so I can definitely see the value in having Regulus not actively working against us. Plus I’m not all that interested in being the only Black Heir. And it's the right thing to do. We’ll start Operation: Restore Regulus right away. I can ask around AIM about curses and their effects on people’s long term health, including the effect of curses on magical cores. I’m sure Hermione will help too.”

“See if you can find any information on transference rituals, particularly rituals involving core magic. I’ve already read everything I can find in the Hogwarts library. In fact, anything involving core magic.”

“Will do, cuz. Take care. And if there’s anything else I should know, please tell me.”

“Of course… Oh. Before I forget, I think Rookwood and Rosier might know something more about the algorithm.”

“Algorithm? What algorithm?”

Oops. Rigel mentally facepalmed. Archie’s habit was contagious.

“Apparently Riddle has been working on an Arithmancy Algorithm that lets him calculate which pairings will produce the most powerful offspring.”

Archie didn’t need to say anything. His look was enough.

“Sorry?” she said apologetically. “It’s just that there’s so much happening, sometimes I forget who I’ve told things to, not that I can tell everything to anyone but you.”

_And me_ , Dom added. 

“The algorithm only matters if the marriage law gets passed. And I’m going to do my best to make sure that it doesn’t. Which reminds me, Dumbledore invited me to his soiree this year.”

“You too? He’s invited Harry and Hermione too.” 

Rigel admired how Archie said this without a hint of embarrassment at forgetting to share this vital fact.

“Guess I’m not the only forgetful person,” laughed Rigel. 

Archie reddened then. “Sorry cuz. But I did write to Uncle James and Aunt Lily about it. I bet you forgot to write and tell Sirius.” 

Rigel apologetically grimaced. Archie just smiled; he knew his cousin so well.

“Please tell me you at least owled Sirius after the task to let him know you’re okay. I can understand that you don’t want him or Uncle James, Aunt Lily and Uncle Remus there because of the ruse, but please tell me you didn’t forget to owl him.”

“Of course I did,” responded Rigel, thinking guiltily of the rather short note she’d scrawled off yesterday, and mentally promising to send a longer letter later. She couldn’t afford to make Sirius suspicious because her poor correspondence habits reminded him too much of Harry.

“Hey, if we’re both at Dumbledore’s soiree, we can just be ourselves,” suggested Archie.

“Rigel needs to do the meet and greet and play the political games.”

“Or not,” Archie replied. “That’s definitely not my forte. Well, we can think about it.”

“Not for long,” said Rigel. “The Easter break is the weekend after next.”

“Whatever we do, we’ll need to be careful. Hermione’s already rather suspicious.”

Rigel didn’t doubt that. Certainly not after the Yule Ball. Hermione had a mind like a steel trap, and the only reason she hadn’t figured out the ruse was because she’d only ever seen the two of them together at the Yule Ball when she was otherwise distracted by the pomp and pageantry of a High Society event. And possibly she didn’t fully appreciate Archie’s metamorphmagus abilities.

“Speaking of Hermione,” Archie added, “I’ve got to go - we’ve got a study session in the library together soon.”

Rigel smiled. “Have fun. Don’t do anything I wouldn’t do,” she teased. 

“Hardly,” laughed Archie. “ We’re _studying_. You always study.”

“Take care.”

“You too.”

\- - - - - - - 

“Puppy!”

“At last!”

Rigel was surprised by the serious looks on the faces of the Weasley twins when they cornered her in the Great Hall after dinner. She’d told Pansy and Draco that she was going to spend some more time in her lab, so they’d gone ahead to the Slytherin common room and wouldn’t be waiting for her. 

“Where have you been?” asked George. 

“We’ve been looking all over for you,” added Fred. “We even considered braving the dungeons to search for you.”

“Recovering,” grimaced Rigel. “I’ve been excused from classes for the week. I slept a lot yesterday, until I finally felt human again. Then I went to my lab to brew. Brewing soothes me,” she explained. 

She didn’t tell them what she was brewing; she hated to think what mischief could occur if the twins got their hands on normal Polyjuice, let alone her long lasting Modified Polyjuice. Rigel told herself that it was prudence, not paranoia, that had instilled in her the recent need to have a supply of her Modified Polyjuice in her potions kit at all times. 

Unfortunately the Modified Polyjuice had a much shorter lifespan; combined with the month it took to brew it meant that she needed to have a cauldron brewing most of the time. 

Thankfully Professor Snape left her to her own devices and didn’t visit her lab; she doubted that she’d be able to hide the distinctive smell of brewing Polyjuice from him, even though she had air freshening and notice-me-not charms surrounding the corner of her lab the Polyjuice cauldron was in. 

“Perhaps we should have been able to tell that you’d been brewing by the distinctive, ah, odour that accompanies you after a brewing session,” suggested Fred.

Actually it had been some time since her free brewing session; she’d had that lengthy mirror call with Archie and dinner since. And given that she’d become rather liberal in the use of odour removal and air freshening charms, it was highly unlikely that any olfactory evidence of her brewing session remained. 

(She’d become rather sensitive to the possibility that she smelt bad after brewing when Draco said she smelt like a sewer and Tahiil thought there was an open drain nearby, not to mention her concerns about the smell of Polyjuice giving away her illicit activities to Professor Snape), 

Still, it never hurt to keep the twins on their toes...

“To be exact, I’ve been free brewing with Professor Snape.” Rigel smiled sweetly. “Are you suggesting that Professor Snape also has a distinctive odour about him?” 

“Not likely,” muttered Fred. 

“Not at all,” said George. “I’m not fond of detention.”

“So what brings you looking for me?”

“Important matters of a confidential nature,” George said airily. 

“We thought the Room of Requirement might be a good place for a discussion,” Fred suggested somewhat more soberly. 

“Lead the way,” Rigel said, wondering what the twins could possibly be up to now.

She was wondering even more when the door to the Room of Requirement opened onto what looked like a mash up of a secure Gringotts vault and the headquarters of a prankster. 

Ready-to-write-on chalkboards lined three of the four walls, with shelves containing a variety of pranking products on the far wall. A horseshoe configuration of tables was covered with supplies of parchment, ink and quills, and three plush swivel chairs (two in Gryffindor red and gold; one in Slytherin green and silver) graced the centre of the horseshoe. 

Rigel raised a questioning eyebrow at the twins. 

“I asked for a secure location for planning,” said Fred, unabashedly, looking around curiously as the door shut with a loud clang and the magic of powerful wards washed over the room. 

“Planning a prank, perhaps?” asked Rigel, gesturing to the pranking supplies.

“The best,” said Fred, grinning evilly as he made his way over to one of the red and gold chairs. “One that will take a lot of planning, but will be so, so, so very _satisfying_ when we pull it off.”

“It’s still early days yet, but we think you’ll enjoy our target,” added George with an evil grin of his own, as he too sat down in a red and gold chair. 

“After all, he’s made your life rather difficult lately,” suggested Fred, “and there’s nothing like a prank to make you feel better.”

Rigel sat down in the green and silver chair, slightly perplexed. The only person who’d really given her grief lately was Riddle, and the leader of the SOW Party was untouchable.

“We will need your advice,” Fred confessed. “We’ve got some ideas, of course, but you’ve got more knowledge of our target than we do. And he absolutely deserves it after what you were forced to do two days ago in the tournament. That wasn’t a test of magical abilities, that was just cruel.”

“We could see the agony that you were in. It was evident on your face. It was horrible to watch - how anyone could think it was entertaining, I don’t know,” said George with disgust, “and it must have been even worse for you.”

Rigel broke into a huge grin. “You’re not thinking of pranking _Riddle_ are you?” She refused to think about the tower climb; thankfully there was very little of it that she could remember, although she knew Dom was as incensed, if not more so than the twins, for the latest task. 

The twin evil grins that met her face were answer enough.

“Wow. That’s just…. Wow. I’m speechless. Thank you. Thank you so much. That’s the nicest thing anyone’s offered to do for me.”

George laughed as he spun his chair around. “Only the son of a Marauder would react like that.”

Rigel rapidly sobered up and stopped the gleefully spinning George. “You will be careful, won’t you?” she asked worriedly. “Riddle’s very dangerous.”

“Hence the reason I asked Hogwarts for a secure pranking plotting room,” said Fred with a smile before he gave her chair a spin. 

“And it’s why we’re plotting with you now. We know we can’t afford to get caught. This is a long term prank. We reckon it’ll take us at least a year, unless we’re lucky,” said George . 

“Besides,” Fred added, “you have the official role as sounding board to the Doctors Weasley, successors to the Marauders. Of course you have to be involved.”

They both fixed her with serious looks. “So what can you tell us about Riddle?” they asked in unison. 

“The more we know about Riddle, the more we can tailor an appropriate prank,” said Fred. 

Rigel thought carefully before she answered. 

“There are some things I can’t tell you; secrets I’m oath bound to keep, and secrets that aren’t mine to share,” she said, thinking of the oath she’d sworn at Malfoy Manor, and Professor Snape’s bargain with Riddle, so like her own. 

“But I will share what I can, and you should feel free to ask me questions. I just might be able to answer them, depending on how you phrase the question, or how I can phrase the answer.”

“Ooo, how Slytherin,” they chorused. 

“It’s hard to know where to start,” Rigel began, “but you should know that Riddle forced me to compete. I didn’t want to have any part in this travesty of a tournament.” Rigel shuddered. 

Both twins looked apologetic at that, remembering their ill advised prank with the tournament sign up sheet. 

“I didn’t want to have anything to do with Riddle’s celebration of blood purity,” she said sourly. “Riddle’s propaganda, the tournament’s propaganda, it’s completely antithetical to what I believe in.”

Rigel held up a hand before they could say anything. 

“No, it’s not your fault I’m in the tournament. Riddle nominated me as soon as the tournament was announced. I refused the nomination. I didn’t know it at the time, but he just ignored my refusal and nominated me anyway.”

Rigel almost laughed at the horrified looks on the twins faces. It felt good to be able to tell her story to people who would understand where she was coming from. 

Sure, Pansy and Draco, even Millie, Blaise and Theo, they were all supportive of her, but they were conflicted. Caught between her and their families, caught between her and their beliefs. 

She continued. “Riddle spent the next month trying to get my agreement. He started with bribes. I refused. I’m not interested in money, just my Potions mastery, and that’s meaningless if I don’t achieve it myself.”

The twins cheered loudly. 

“He tried to threaten my family, my father and Harry. But his threats were empty. He doesn’t understand me or my relationships. I still refused.”

“Wow,” whistled George. 

“So how come you’re competing?” Fred asked. 

“Riddle finally made me an offer I thought was too good to refuse,” Rigel said bitterly. “And he would have entered me regardless of my wishes anyway.”

The twins were wide eyed. 

“What?” asked George. 

“Or can’t you tell us,” suggested Fred. 

She thought she’d better put them out of their misery and not draw it out any longer. 

“Riddle and I swore Unbreakable Vows, but there was no confidentiality constraint included, so I can tell you. Some of my housemates already know. For my participation in his tournament, Riddle agreed to disavow the Death Eater attacks on muggleborns. And if I win, there will be no more legislation discriminating against non-purebloods in employment, healthcare, and marriage, would not come to pass. I don’t really understand why he so desperately wanted me to compete, but I swore an Unbreakable Vow to compete in all tasks to the best of my ability.”

“But isn’t the marriage law currently being considered by the Wizengamot?” asked Fred. 

“Yes,” replied Rigel sourly. “And when I questioned Riddle about that, he condescendingly told me to be careful when wording agreements and reminded me that he wasn’t bound yet.”

She shrugged. “Nothing I can do about it now, but it’s certainly something I’m not going to forget anytime soon. I can only hope that there’s a delay with the marriage law before the Wizengamot. But Riddle controls the timetable for both the Wizengamot and the final task.”

“Well, my brother,” said George excitedly, “mucking up the marriage law could provide an admirable prank on Riddle. So what else can you tell us about him?”

“Well, Riddle’s a bigger hypocrite than you think.”

Fred scoffed. “How is that possible? The man’s a Dark Pureblood politician.”

“Not quite,” said Rigel with a wry smile. “Politician - tick. Dark - tick. Pureblood - no.”

“Noooo,” gasped Fred. “Surely no one could possibly be that audacious.”

“Isn’t the man a Parselmouth? That’s a Dark Pureblood gift,” declared George. 

Rigel smiled. “I couldn’t possibly say if he’s a Parselmouth. Oaths and things.” Rigel smiled inwardly. That comment didn’t even tweak the oath she’d sworn at Malfoy Manor. But what she said next would surely confirm her point to the twins, within the bounds of her oath. 

“But I _can_ confirm that I’m not the only Parselmouth in Britain, and while I’m not a Dark Pureblood,” she said with a wry smile, “neither is the other British Parselmouth I know.” 

There were multiple hidden meanings behind her wry smile. She was confident that the twins would pick up on her allusions to Parselmouth Riddle, and not the rest of her statement, which, although misleading, was all very true. _H_ _er_ magic was mostly neutral, her politics certainly not those of the SOW party. And Archie, the real Rigel Black, was not Dark, neither magically (being a Neutral-Dark mix), nor politically. 

The twins were friends; she might have to lie to maintain the ruse, but she preferred the truth, albeit even if only partial or obfuscated, where possible. 

“Besides, I have done research into my Parselmouth gift, and I can assure you it’s not limited to Dark Purebloods.” 

Rigel couldn’t help but smile inwardly as she imagined the look on her father’s face should he ever be made aware that the Parselmouth ability was a magical inheritance from the Light Pureblood Potter family from their Peverell ancestors.

“I have also done research into Tom Riddle’s family,” and here she tried not to sound too stalkerish or obsessed, “and Riddle is not a family in any of the Books of Gold, Silver, or Bronze.”

Rigel smiled at their gobsmacked expressions. It was hard to figure out which twin was sporting the lowest dropped jaw, or who had the widest eyes. 

“But, but, he’s Lord Riddle,” stammered George. 

“He’s only a Lord because he says so and people accept it.” She ignored that Riddle’s powerful magic was considered “lord level”. She would warn the twins about that later.

“Riddle doesn’t hold an Order of Merlin First Class, and he’s not the Lord of a Book of Gold, Silver or Bronze family. His maternal family is an extinct Book of Gold family, the Gaunts. His mother was Merope Gaunt, called a squib by her father, Riddle‘s grandfather. As for Riddle’s father,” and here she paused for emphasis, for dramatic impact, to line the quaffle up with the goal hoops before shooting. 

“Riddle’s father was a _muggle_ , Tom Riddle, son of the muggle squire of Little Hangleton, Thomas Riddle. So called Lord Tom Marvolo Riddle, the power behind the SOW party and the Minister, is a Halfblood. He might be magically powerful, but according to the SOW party definitions, he is a Halfblood. And a hypocrite.” 

And so am I, she thought sourly. Both a halfblood and a hypocrite. But she was not ashamed of being Halfblood Harry Potter, and if she could win the tournament before the marriage law was passed, the constraints on Halfbloods and muggleborns would lessen. 

There was silence from the twins. 

“You can confirm what I’m saying with Dumbledore, if you don’t believe me,” she said. “Riddle grew up in an orphanage, and Dumbledore was the teacher who introduced him to Hogwarts. Apparently he was originally thought to be a Muggleborn, but when his Parselmouth ability became known, his magical ancestry was discovered.”

“I never would have guessed,” said George. 

“Yeah, who’d have ever thought it?” asked Fred. 

“That Riddle is a prankster!?!” they exclaimed together. 

“And what a prank it is! Pranking the whole of Dark Pureblood Society. That’ll be a hard prank to beat,” mused Fred. 

“But we can do it!” exclaimed George. “For we are the Doctors Weasley!”

“Successors to the Marauders!” cried out Fred. 

“And we will be the greatest pranksters the wizarding world has ever seen!” concluded George with a smile. 

Rigel started to laugh. The twins joined in, wildly spinning their chairs around. This was why she loved the Weasley twins. They knew how to cheer her up. 

“So how can we use this?” asked George once they’d calmed down a bit. 

“That’s the difficulty,” said Rigel. “I don’t know if we can. I’ve already spoken to Dumbledore about this, and he thinks that Riddle would claim both his parents as Gaunts - to be the child of a brother and sister would be more palatable than to have a muggle patent, apparently.”

“Well, we’ll put it to one side for a moment. Knowledge is never useless,” said George. 

“You remind me of Uncle Remus,” Rigel said with a smile. “That’s just the sort of thing he’d say.”

“How is Professor Remus these days?” inquired Fred. “It was a shame to see him go. I enjoyed his dueling class.”

“And Professor Dawlish can be brutal,” added George. 

“Uncle Remus is doing well,” said Rigel. “He’s tutoring some of the kids in the Lower Alleys, in between his work for Marauders Inc.”

“Lower Alleys, huh,” said Fred. “Mum and Dad have always warned us to stay clear of anywhere other than Diagon Alley. Bill too.”

Rigel could see why Bill might have warned his siblings to stay out of the alleys. Nobody liked having their secrets threatened. And secrets aside, letting the twins loose in the Lower Alleys would most likely result in chaos of some form. 

Still, she thought that the twins would enjoy the freedom of the alleys, and on balance, Bill and Harry’s Lower Alleys lives notwithstanding, she thought the alleys would benefit. At the very least, they’d keep Leo on his toes. 

“I think the Lower Alleys are unfairly castigated,” Rigel said mildly. “Harry spends time in the alleys looking for ingredients at apothecaries, and her friend Hermione Granger interned at the Maywell clinic in the alleys last summer. Anyway, we’re getting off track here.”

“Quick question. If Riddle‘s a halfblood, does that mean he’s going to be caught by the marriage law?”

Rigel laughed. “Fred, that’s just beautiful. That would be so good. And while I don’t know the latest details of the marriage law, I _have_ heard that Riddle’s developed an algorithm and he’ll be personally matching all the Dark Pureblood heirs to get the most magically powerful offspring.” 

“I know,” said George mischievously, “we’ll prank the algorithm. Wouldn’t it be hilarious if the algorithm matched every dark Pureblood heir with Halfblood Tom Riddle.”

“Almost as fun as a halfblood or muggleborn winning Riddle’s precious tournament,” cackled Fred. 

Rigel couldn’t stop herself from laughing. If only the twins knew…. She had to pull herself together. She had to be careful. She couldn’t afford to give herself away. 

Still, it just felt so _good_ to be able to laugh at all this. She’d been under the pressure of the tournament, under pressure from Riddle, from the ruse, from balancing the competing interests of her friends and their families against her interests and her family’s interests. She’d been under pressure for just so long. 

“Thank you,” she gasped through tears of laughter. “I needed this. I really needed this.”

“So we’re agreed, then? We’ll make plans to prank Riddle’s algorithm?” Fred asked in confirmation. 

“Absolutely,” declared Rigel. 

“Most definitely,” said George. 

“Then I solemnly declare that the next-“

“-and most important,” George interjected. 

“-prank of the Doctors Weasley will be the pranking of Riddle’s Algorithm.” said Fred in an officious tone. 

“Now, Fred, there’s no need to channel Percy.”

“How is Percy?” Rigel asked, before the twins started teasing their brother in absentia. 

“Doing really well as a trainee lawyer from what Mum says,” said Fred. 

“I wonder what Percy thinks of the marriage law,” mused Rigel. “It would be good to get a legal perspective.”

“And to have a lawyer bail ready to us out if this goes belly up,” muttered Fred. 

“None of that,” chided Rigel. “You’re the Doctors Weasley and I’m the son of a Marauder. We’ll do our research and our planning. We won’t get caught. Besides,” she said, “while Riddle does have reasons for the marriage law beyond power hungry megalomania and an apparent fetish for extreme micromanagement, I’m convinced there’s an alternative solution, and I’m going to find it.”

They looked at her blankly. 

She sighed. “What do you know about the Fade?”

“Not a lot,” admitted George. 

“It’s not been much of an issue for the Weasley family,” said Fred. “So yeah, I don’t know much about it. Although I do know that Hermione was looking into it.”

Rigel summarised Hermione’s findings as succinctly as she could. It was getting late, and while she had the Potter Invisibility Cloak and the Marauders map, and Snape would most likely turn a blind eye, she preferred to avoid curfew violations if possible. 

They agreed on a range of things to investigate before meeting again. Rigel left the Room of Requirement with a longer to do list, but nevertheless happy. 

She liked being busy. Which was just as well, because with the tournament, the twins, Dumbledore’s soiree, her first aid kit, free brewing, the Fade, Regulus, Riddle, and the ruse, she was going to be very busy indeed. 

**Author's Note:**

> TBC...
> 
> I'm feeling a bit nervous posting chapters as I go, so fingers crossed that my muse doesn't desert me until this is finished. (There's a few ideas I want to explore, but I just wanted to share this with everyone sooner rather than later).


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